What was the name of Genghis Khan's legal code?

Genghis Khan’s legal code was called the Yassa, also spelled Yasa or Jasagh. It was associated with the rules, customs, and administrative orders established under his authority after he united the Mongol tribes.

The Yassa was not a surviving law book in the modern sense. No complete original text has been found, and much of what historians know comes from later Persian, Arabic, and European accounts. It likely combined older Mongol steppe customs with commands issued by the khan.

The code dealt with matters such as military discipline, loyalty, hunting regulations, theft, messenger safety, and relations between tribes. Its provisions helped turn a loose collection of rival nomadic groups into a more coordinated imperial state.

A common mix-up is to treat the Yassa as equivalent to Islamic sharia or a single written constitution like the Code of Hammurabi. The name and contents are also sometimes attributed too narrowly to Genghis Khan personally, since later Mongol rulers continued developing and applying imperial rules.